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Systematic Mapping of Bedrock and Habitats along the Florida Reef Tract—Central Key Largo to Halfmoon Shoal (Gulf of Mexico)

USGS Professional Paper 1751

by Barbara H. Lidz, Christopher D. Reich, and Eugene A. Shinn

Introduction: Table of Contents Project Overview Project Objective Geologic Setting Primary Datasets Primary Products - Overview Maps & Evolution Overview: Introduction Depth to Pleistocene Bedrock Surface Reef & Sediment Thickness Benthic Ecosystems & Environments Sedimentary Grains in 1989 Summary Illustration Index Map Evolution Overview Tile-by-Tile Analysis Organization of Report Tiles: 1, 2, 3, 4, 5, 6, 7/8, 9/10, 11 Summary Acknowledg- ments References Disclaimer Related Publications

Summary Summary Modern Reefs and the Rock Record Fate of the Present Coral Reef Ecosystem Fate of the Present Coral Reef Ecosystem: We do not know whether the decline of Florida's coral reefs, as observed in the field and detected in the sands, is due to natural change alone or whether human activities are a contributing factor of some consequence. Certainly, leisure diving, ship groundings, farmland runoff, nutrient influx, airborne contaminants, groundwater pollutants, fish exploitation, and many other human pursuits are impacting the Florida reef ecosystem to some degree. But reefs are being affected globally, even reefs that are distant from civilization (e.g., Wilkinson, 2000). Steps are being taken to protect reefs and other submerged lands in areas comprising 1,469,263 hectares (3,630,500 acres) worldwide, where the U.S. Department of Interior (DOI) has jurisdiction (Koltes, 2004). Three DOI agencies oversee these areas. The U.S. Fish and Wildlife Service manages National Wildlife Refuges. The National Park Service administers National Parks, National Historic Parks, and National Monuments. The Office of Insular Affairs supervises one area, Wake Atoll. Reefs in the Florida Keys National Marine Sanctuary are protected under authority of the National Oceanic and Atmospheric Administration, U.S. Department of Commerce. Human activities are but one assortment of stresses to coral reefs. Natural changes are occurring as well. Among the changes, coral diseases are on the rise in frequency and number (e.g., Edmunds, 1991; Aronson and Precht, 2001; Sutherland et al., 2004). Iron influx is spurring growth of red tides (Lenes et al., 2001). Water-temperature extremes, very hot in summer (e.g., Glynn, 1984) and very cold in winter (Roberts et al., 1982), are stressing corals. Sea level is rising (e.g., Albritton et al., 2001), which in Florida is increasing tidal exchange of deleterious inshore bay and cold Gulf of Mexico waters with the reefs. Relative to the late 1960s, the quantity of African dust influx to the Florida-Caribbean region has increased in concentration (Fig. 5). The dust carries microbes harmful to human health and marine ecosystems (Muhs et al., 1990; Shinn et al., 2000; Griffin et al., 2001; Griffin et al., 2002). Even knowing some of the highly probable causes of coral reef decline, the question of mitigation remains. Stressor sources are atmospheric, terrestrial, and oceanic. By their nature, these sources are largely uncontrollable. In terms of efficacy, attempts to manage them have been likened to placing screen doors in a submarine (Jameson et al., 2002). Should efforts be successful in positively identifying and effectively mitigating local human impacts, results still will not deter declines due to natural stressors aggravated by man-made stressors entering through the screened-door sources. As has been shown throughout this report, developing a comprehensive evolutionary history for the south Florida shelf has improved our understanding of processes that have governed the structure, function, and health of past coral reef ecosystems in the area. The same natural processes will construct and nurture reef ecosystems of the future. We cannot predict the fate of the present coral reefs, in Florida or elsewhere. But we know from the biogeologic record that, given a continuing fluctuation of sea level, the life-and-death cycle of the coral reef ecosystem will continue. continue to: Acknowledgments

Coastal & Marine Geology Program > Center for Coastal & Watershed Studies > Professional Paper 1751